quality

Set the print quality.
[read/write property] quality([out, retval] int *quality) quality([in] int quality)
This property sets the print quality: This setting is only relevant for GDI printing, i.e., for non-PostScript printers, or if forceGDI is true. It is ignored when XpdfPrint generates PostScript code.

resetParams resets this to its default value, which is to use the driver's default quality.

VB6:
pdf.quality = 3
printerSupportsQuality
resetParams